Jack Sepkoski

Joseph John Sepkoski Jr. (July 26, 1948 – May 1, 1999) was a University of Chicago paleontologist. He was a scientist who studied fossils to learn about life in the past.

Sepkoski worked closely with David Raup to study how life on Earth has changed over millions of years, especially during times when many species disappeared suddenly.

Sepkoski and Raup used numbers to understand patterns in the fossil record. They found that big events, called mass extinctions, had happened several times in Earth's history. These events caused many plants and animals to die out all at once. One of these big events was the extinction of dinosaurs that happened about 66 mya.

Their most important discovery was what they called the "Big 5" — the five biggest mass extinctions in Earth's history. These events shaped how life evolved and why some animals and plants exist today. Sepkoski’s work helps scientists understand how Earth’s ecosystems have changed and what might happen in the future.

Life and work

Joseph John Sepkoski Jr. was born in Presque Isle, Maine. He studied at the University of Notre Dame and later earned a Ph.D. from Harvard University under Stephen Jay Gould. Sepkoski taught at the University of Rochester before joining the University of Chicago, where he became a professor.

Sepkoski is known for his work on marine animal fossils. He made important collections of data that help scientists learn about changes in life on Earth over time. In 1981, he described three main groups of marine animals, called Evolutionary Faunas. These groups appeared and disappeared in a pattern over millions of years. He was married to paleontologist Christine Janis, and had a son, historian of science David Sepkoski.

Awards

In 1983, Jack Sepkoski got the Charles Schuchert Award from the Paleontological Society. He was also chosen to be a foreign member of the Polish Academy of Sciences.

Selected publications

Joseph John Sepkoski Jr. wrote many important papers about fossils. He studied how life on Earth has changed over time. His work looked at how groups of animals appeared and disappeared in the oceans. He also researched big events that caused many animals to die out suddenly.

His publications appeared in respected science journals and books. He shared his discoveries with other scientists around the world.